1. Field of the Invention
The present invention relates generally to an improved communications system and in particular to a method and apparatus for establishing and maintaining a communication session. Still more particularly, the present invention provides a method and apparatus for a distributed processing manager using Session Initiation Protocol.
2. Background of the Invention
Session Initiation Protocol (SIP) is an application-layer control protocol for transporting call setup, routing authentication and other feature messages to endpoints within the IP domain, whether those messages originate from outside the IP cloud over PSTN resources or within the cloud. These sessions include Internet multimedia conferences, Internet telephone calls, and multimedia distribution. Members in a session can communicate via multicast, via a mesh of unicast relations, or a combination of these. SIP can be used to initiate sessions as well as invite members to sessions that have been advertised and established by other means.
SIP is a text-based protocol that uses the ISO 10646 character set in UTF-8 encoding. A SIP message is either a request from a client to a server or a response from a server to a client. Both of these types of messages contain a start line, one or more header fields, or xe2x80x9cheadersxe2x80x9d, an empty line indicating the end of the header fields, and an optional message body.
In processing a SIP message, different SIP message headers have different characteristics with respect to the frequency of occurrence in SIP messages. Some headers, such as a xe2x80x9cToxe2x80x9d header, are generic headers that appear only once while other headers, such as xe2x80x9cViaxe2x80x9d headers, are generic headers that can appear any number of times. The xe2x80x9cViaxe2x80x9d headers, for example, provide information pertaining to the route through which a SIP communication must pass between SIP clients.
Headers, such as xe2x80x9cCallerIDxe2x80x9d, xe2x80x9cToxe2x80x9d, and xe2x80x9cFromxe2x80x9d headers are essential for establishing the context of the SIP message. However, from the viewpoint of an application program, maintaining other context and state information related to a session, such as storing a long sequence of Via headers, detracts from the essential task of providing a distributed application with particular functionality.
Therefore, it would be advantageous to have an apparatus and method for managing application non-essential information, such as routing information. It would further be advantageous to have an apparatus and method that presents an application program with a simplified SIP environment.
The present invention provides an apparatus, method, and system for communication using Session Initiation Protocol (SIP). A data processing system, according to the present invention, contains a network interface and a SIP client manager that receives SIP messages through the network interface. The SIP client manager contains a SIP management module and an X-SIP client module. The SIP management module contains a SIP message modifier for modifying incoming messages and outgoing messages in accordance with context information or state information for a session associated with a SIP message. The SIP management module also contains input/output controllers for receiving, sending, and forwarding SIP messages.
The X-SIP client module contains an input/output controller for receiving and sending SIP messages and a SIP application programming interface (API) for handling SIP messages for a SIP-enabled application. The X-SIP client module performs conversion of client application formatted messages, into X-SIP messages, i.e. modified SIP messages, and vice versa. The SIP management module and the X-SIP client module communicate via a socket for transmitting these messages between the SIP management module and an X-SIP client module, thereby creating a distributed SIP client architecture for managing SIP information.
When SIP messages are sent from a client application to a SIP server, the message from the client application is first received by the X-SIP client module. The X-SIP client module converts client application messages into simplified SIP messages containing, for example, the xe2x80x9cTo,xe2x80x9d xe2x80x9cFrom,xe2x80x9d and the xe2x80x9cCallerIDxe2x80x9d headers. The simplified SIP message is forwarded to the SIP management module which performs context management to determine routing information for the simplified SIP message. The SIP management module adds the routing information to the simplified SIP message to thereby create a non-simplified SIP message. The non-simplified SIP message is then forwarded to a SIP server via an IP network.
When SIP messages are received from a SIP server, the SIP message is first received by the SIP management module. The SIP management module strips the SIP message of the routing information and stores the routing information in memory. The resulting simplified SIP message is forwarded to the X-SIP client module. The X-SIP client module then converts the simplified SIP message into a client application message.